412 MABEL BISHOP 



of chorda tympani and lingual nerves identified the external 

 pterygoid muscles (fig. 18). The developing parotid glands, 

 and therefore the masseter muscles, the submaxillary and sub- 

 lingual glands were identified (figs. 18, 19). These were then 

 readily found on the inner side of each head member. Here the 

 masseter, external pterygoid muscles, and parotid glands are 

 quite independent for each head (figs. 18, 19), but the submaxil- 

 lary and subhngual glands terminate in a conjoined condensation 

 of connective tissue (figs. 18, 19). 



Moreover, by tracing Meckel's cartilage on the normal side 

 of head A and head B from symphysis mentis to its proximal 

 termination, the malleus, there is established another definite 

 landmark. Meckel's cartilages of the median region (i.e., the 

 left one of head A and the right one of head B) were then traced 

 craniad in similar planner and were found to converge and fuse 

 in the midline at about the level of the common root of the two 

 tongues, thus forming conjoined Meckel's cartilages at or near 

 their otic ends (fig. 17). The model of the chondrocranium 

 (not figured) shows a thickened knob of cartilage at this point 

 which undoubtedly represents united periotic cartilages. The 

 sections show this cartilage extending through several milli- 

 meters surrounded by diffuse connective tissue and more or less 

 undifferentiated muscle masses (fig. 16). 



Lying in the midline of the monster between this conjoined 

 periotic mass and the median external auditory meatus is an 

 elongated strand of cartilage which topographically identifies 

 it as conjoined cartilage around these fused external meatuses 

 (figs. 18, 19). This interpretation is further supported by the 

 relationship of the cartilage to the parotid glands and masseter 

 muscles which flank it on either side, remembering that the 

 midline of the monster represents juxtaposed external surfaces 

 of the two heads. The glands and muscles are then in normal 

 morphological relationship to the conjoined external auditory 

 meatal cartilages and the oral cavity of each head. 



A mass of cartilage representing united internal ear capsules 

 of the conjoined heads, and probably involving the sphenoids, 

 too, lies between the fused periotic cartilages and basis cranii 



